UT-Arlington scientist’s research could have impact on a pressing problem: plastic waste

A University of Texas at arlington scientist’s research could have an impact on one of the world’s most pressing problems: plastic waste.

Plastic waste has become a major environmental concern. From 1950 to 2015, more than 8,000 million tons of plastic was produced and only 6–7% was recycled, according to a 2017 study in ScienceAdvances. More than half of the waste went straight to landfills.

Public health experts are starting to dig into the effects of microplastics and the potential impacts they may have on human health. A process known as pyrolysis is seen by some researchers as a way to reduce plastic waste.

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Essentially, a material – in this case, plastics – is placed into a chamber with no oxygen and heated until the material breaks down. Once the plastics are heated in this process, they form an oil called pyrolysis oil.

That’s where Dr. Kevin Schug, a professor of analytical chemistry at UTA, comes in. He recently published a paper in the Journal of Chromatography A that aimed to identify two common types of plastic compounds, polyethylene (PE) and polypropylene (PP), in pyrolysis oils.

There are some potential benefits to this process, according to Schug.

Mechanical recycling, the most common form of recycling, requires separating plastic waste. And it can only be done on Type 1 and Type 2 plastics – basically only soda bottles, water bottles and milk jugs.

But with the pyrolysis process, any plastic can be turned into pyrolysis oil for reuse and refining – some of it can be reused as plastic, or some of it can be used as fuel. This could potentially reduce their abundance in the environment, said Dr. Petr Vozka, an analytical chemistry professor at California State University in Los Angeles, who wasn’t involved in Schug’s research.

However, pyrolysis oils are a mixture of thousands of plastic compounds, including PE and PP. This makes it difficult to determine how to refine the oils. Being able to consistently identify any of these compounds is a key step to making pyrolysis of plastics more effective.

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Schug cautioned against using pyrolysis oils to only create fuel, as these oils would create greenhouse gasses. Solar energy and wind energy are ultimately more sustainable energy sources than pyrolysis oils, according to Schug.

But he argues the process could be a “cog in the wheel” of a more sustainable future. A better goal, instead of using pyrolysis oils as fuel, would be to use them to create new plastic which would divert plastic waste from the environment, according to Schug.

Vozka said people often claim that pyrolysis can reduce greenhouse gas emissions, though he doesn’t think that is the case. But for countries that need plastic waste management systems, like India or Egypt, pyrolysis can provide an alternative while greener technologies are developed, Vozka said.

Not everyone believes that pyrolysis is a sustainable or climate friendly alternative.

Dr. Veena Singla, an adjunct assistant professor of environmental health sciences at Columbia University, said pyrolysis oils won’t significantly reduce our need for fossil fuels. And the best solution will always be to keep crude oils in the ground while looking for more sustainable materials.

Jane Dell is a chemical engineer and National Geographic Explorer, an international group of high-level scientists and experts who receive funding and support from the National Geographic Society. She also founded The Last Beach Cleanup, a nonprofit that brings attention to plastic pollution.

She agreed with Singla via email. Economically, the incentives for creating new plastics from raw materials and crude oil will always be cheaper than repurposing plastics through pyrolysis, according to Dell.

And Dell pointed to the EPA’s draft national strategy to prevent plastic pollution, which states that turning plastic waste to fuel is not considered recycling.

Complex pyrolysis

One of the reasons pyrolysis presents a challenge for sustainability efforts is because of pyrolysis oils.

Once the plastic compounds are broken down into an oil, determining which compounds come from which plastics is difficult. This makes picking the right refining process a challenge.

To tackle this problem, Schug and his colleagues used non-traditional separating methods to identify two common plastic compounds, PP and PE.

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They did this by using supercritical fluid chromatography (SFC) and ultraviolet (UV) detectors. In Schug’s study, SFC was used over more traditional chromatography methods because the process can better analyze heavier compounds.

The process also uses a superheated and pressurized form of carbon dioxide, which is less toxic than other chemicals used in chromatography methods.

Schug said since this method successfully identified PP and PE oils, it could help determine which compounds in mixed plastic waste could have the most benefits for reuse.

He also said other compounds should be tested to determine their unique signatures, especially if these oils are to be further refined.

Though pyrolysis may not reduce greenhouse gas emissions, the process may help reduce plastic waste accumulation that has already entered the environment, according to Vozka. He said Schug’s research can help pioneer these efforts.

“Certainly, plastics in the environment is a huge problem, and if we can have more ways to divert plastic waste into usable products, then that’s a major benefit for our environment,” Schug said.

Jordan Chapman reports on science for The dallas Morning News as part of a fellowship with the American Association for the Advancement of Science.

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